1. Field of Invention
The present invention relates to a liquid crystal display device and a method for manufacturing it. More particularly, the present invention relates to a liquid crystal display device comprising the display component of an information equipment terminal, television or home appliance product, and a method of manufacturing the liquid crystal display device.
2. Description of Related Art
In recent years, as information equipment has become more compact and lightweight, display devices to be mounted on such equipment have been sought which consume less power. Liquid crystal display devices using the twist nematic (TN) mode are utilized as reflective displays in small display capacity equipment, while liquid crystal display devices using the film compensate super twist nematic (FTN) mode are utilized in the mid-range display capacity equipment. Furthermore, uses wherein an information input apparatus such as a tablet or the like is included on the reflective-type display are also expanding. All these reflective-type liquid crystal display devices require brightness and good visibility.
However, TN-format and FTN-format liquid crystal display devices that use conventional polarizing plates have low light utilizing efficiency. A problem then arises in that the TN- and FTN-format liquid crystal displays become dark when made reflective. Moreover, an extremely dark display results when an information input apparatus such as a tablet or the like is included. In addition, because a reflective plate is placed over the polarizing plate on the back surface of the substrate to make a reflective model with the TN format or FTN format, double images occur in the display, small characters are unclear, and there are problems with visibility.
On the other hand, bright reflective-type displays that do not use polarizing plates have come to be developed recently. For example, a liquid crystal display device that uses a polymer dispersion liquid crystal in which liquid crystal and polymer are mutually dispersed, and which is controlled so that the display is transparent when an electric field is impressed and the light is scattered when no electric field is impressed has been disclosed (Japanese Laid-Open Patent Publication 58-501631). Other liquid crystal display devices, which are controlled so that the light is scattered when an electric field is impressed, and the display is transparent or light is absorbed when no electric field is impressed have been also been disclosed (European Patent Application EPO 488116A2, Japanese Laid-Open Patent Publication 4-227684, Japanese Laid-Open Patent Publication 5-119302).
In particular, in the polymer dispersion-type liquid crystal display device using a polymer dispersion liquid crystal, disclosed in European Patent Application EPO 488116A2, in which the liquid crystal and polymer are mutually orientation dispersed, it is possible to also use the electrodes as light reflecting surfaces because no polarizing plate is used. In this case, good visibility, high precision and brightness, which cannot be achieved in the TN and FTN modes that require polarizing plates, are obtained, and it is possible to obtain a reflective display with superior display quality.
However, with the conventional art that has been disclosed with regard to polymer dispersion-type liquid crystal display devices that use polymer dispersion liquid crystal in which the liquid crystal and polymer are mutually orientation dispersed, no control method for the light scattering properties that influence the field angle properties and brightness has been disclosed. In particular, when the device is used as a reflective-type display, the influence that the usage environment and the display positioning has on the display quality is large, but no design method for a liquid crystal display device which takes these points into consideration has been disclosed.
When the liquid crystal display device is mounted on portable equipment, the usage environment can roughly be separated into indoor and outdoor environments. Outdoors, a brightness approximately 100 times that of a general office exists. Because the scattering-type reflective display has an extremely bright display state, brightness is not an important factor in a design that assumes an outdoor environment. In contrast, in a design that assumes an indoor environment, brightness is an important factor. Furthermore, efficient scattering is required in environments that have a large incident light component coming from the upward direction.
In addition, when the liquid crystal display device is mounted on portable equipment, control of the viewing angle properties is necessary to provide privacy protection.
In consideration of the foregoing, it is an objective of the present invention to provide a liquid crystal display device that controls the light scattering properties of a polymer dispersion-type liquid crystal display device using a polymer dispersion liquid crystal with the liquid crystal and polymer mutually orientation dispersed such that the display is particularly bright in a specific direction, and for which the contrast ratio is high. It is also an objective of the present invention to provide a method for producing such a device.